碱金属Na对黑液水煤浆焦-CO2气化特性的影响

黑液中富含大量的碱金属Na及其化合物,这些碱金属将在黑液水煤浆焦气化过程中起到催化气化的作用.为了研究黑液水煤浆焦-CO2催化气化反应特性,采用XRD、SEM和热重分析技术对黑液水煤浆焦和普通水煤浆焦CO2催化气化实验进行分析,得到了焦炭表面孔隙分布情况、煤浆焦样和气化后残渣XRD分析结果,以及等温条件下气化反应时碳转化率数据.试验结果表明:黑液水煤浆焦表面密集分布很多"斑点"和微孔,说明碱金属Na盐在焦碳表面形成了活化中心点,它们在气化过程中起到催化作用;碱金属Na使焦样表面具有更强的反应位,削弱C-C键的强度,使气化反应更容易进行;同时由于碱金属催化剂在高温气化时将与煤中矿物质反应生成惰性物质,从而可能削弱催化效果.从黑液水煤浆与普通水煤浆XRD晶相分析中可以看出碱金属Na盐主要以氯化钠、硅酸钠形式存在,气化反应后生成的晶相组成主要是霞石和微斜长石.

Catalytic Influence of the Alkali-Metal Na on the CO2-Gasification of Coal Black Liquid Slurry Char

The coal black liquor slurry (CBLS) contains plenty of sodium and sodium compounds which can promote the C-CO2 gasification process as catalysts. In order to study the CBLS char CO2-gasification characteristics with the alkali-metal catalysis existing in it, the CO2-gasification experiments of CBLS char and coal water slurry (CWS) char were analyzed by the thermobalance, XRD and SEM. Through which the structural properties of two kinds of chars, XRD patterns of their samples, gasification residues of CBLS and CWS chars as well as their carbon conversion data were obtained. It reveals that there are many spots and micropores on the surface of CBLS char, which play a key role for catalyzed gasification process, and more importantly, the Na in CBLS can enhance the reaction-potential, weaken the C-C bonds and enhance the gasification reaction rate. However under the high temperature of gasification, the alkali catalyzer would react with mineral in coal and forms inert substances which could weaken the catalytic effect on the gasification process to some extent. The XRD analyses of the dry samples of CBLS and CWS show that the alkali Na salts in CWS and CBLS exist in the form of NaCl and sodium silicates mainly, and after gasification, they turn into nepheline (Na6K1.2Al7.1Si8.9O32) and microclion (KAlSi3O8).